US 8020619 B1
Methods for severing tubing having a cable extending along its length include lowering a first cutting torch into the tubing to a desired location, igniting the first cutting torch, and directing cutting fluids in a circumferential arc to form a first cut in the tubing and sever the cable. A second cutting torch can be lowered and positioned relative to the first cut, and ignited to direct cutting fluids radially to cut the tubing all around the circumference, enabling retrieval of the tubing. The need for precise positioning and alignment of the torches to sever both the cable and tubing is thereby eliminated.
1. A method of severing tubing in a well, the tubing having a cable extending along a length of the tubing, the tubing having a circumference, comprising the steps of:
a) lowering a first cutting torch into the tubing;
b) positioning the first cutting torch at a desired location within the tubing;
c) igniting the first cutting torch so as to produce first cutting fluids;
d) directing the first cutting fluids from the first cutting torch in a circumferential arc in a direction of the cable, so as to make a first cut of a portion of the tubing circumference and sever the cable with the first cutting fluids from the first torch;
e) lowering a second cutting torch into the tubing;
f) positioning the second cutting torch relative to the first cut;
g) igniting the second cutting torch so as to produce second cutting fluids; and
h) directing the second cutting fluids radially so as to cut the tubing all around the circumference.
2. The method of
3. The method of
4. The method of
5. The method of
6. A method for severing a tubular string having a cable extending along a length thereof, comprising the steps of:
a) lowering a first cutting apparatus into the tubing;
b) actuating the first cutting apparatus to form a first cut in the tubing and sever the cable;
c) lowering a second cutting apparatus into the tubing; and
d) actuating the second cutting apparatus to form a second cut in the tubing.
7. The method of
8. The method of
9. The method of
10. The method of
11. The method of
12. The method of
The present invention relates to methods for severing tubing in downhole wells.
In oil and gas wells, fluids are typically produced to the surface by way of production pipe or tubing. The production tubing extends from the well head at the surface down the well to the production zone.
From time to time, it is desired to pull the production tubing from the well. For example, if the well ceases to produce economically, then downhole components, such as the production tubing, can be salvaged and used in another well.
If the production tubing cannot be pulled from the well, then it is frequently desirable to cut or sever the tubing and salvage at least part of the tubing. To cut the tubing, a torch is lowered into the tubing. A particularly effective cutting tool is my radial cutting torch, described in U.S. Pat. No. 6,598,679. The torch creates cutting fluids that project in a radial direction all around the circumference of the tool and severs the tubing with a circumferential cut. The production tubing located above the cut can then be pulled from the well.
In some wells, cables or control lines are run down the well. Some cables or lines control equipment located downhole. For example, the well may be provided with an electric submersible pump, which pump utilizes a power cable. As another example, a safety valve may be located downhole; the safety valve uses a hydraulic control line on the outside of the production tubing. The cables or lines are attached to the outside of the production tubing by clamps.
Cutting the production tubing with the exterior cable or line is difficult. Simply cutting the tubing typically leaves the cable intact, wherein the tubing portions, the upper portion and the lower portion of tubing, are tied together with the cable. Cutting the cable is difficult because the tubing effectively shields the cable from the cutting torch inside of the tubing.
In the prior art, cutting the cable is a two-step process. First, a first torch is lowered into the production tubing to make a first cut through the production tubing. This creates an opening in the tubing and exposes the cable to the inside of the tubing. Then, the first torch is removed and a second torch is lowered into the production tubing to cut the cable through the opening in the tubing. However, aligning the second torch with the tubing opening is difficult. A misalignment of the second torch results in the cable surviving intact and uncut; another torch must be lowered into the tubing for another attempt. Failing to cut the cable with the second torch increases the cost of salvaging the production tubing. Thus, it is desired to cut the cable without the need to align a torch with an opening in the pipe.
The present invention provides a method of severing tubing in a well. The tubing has a cable extending along a length of the tubing. The tubing has a circumference. A first cutting torch is lowered into the tubing. The first cutting torch is positioned at a desired location within the tubing. The first cutting torch is ignited so as to produce first cutting fluids. The first cutting fluids are directed from the first cutting torch in a partial circumferential arc in the direction of the cable, so as to make a first cut of the tubing circumference and to sever the cable with the first cutting fluids. A second cutting torch is lowered into the tubing. The second cutting torch is positioned relative to the first cut. The second cutting torch is ignited so as to produce second cutting fluids. The second cutting fluids are directed radially so as to cut the tubing all around the circumference.
In accordance with one aspect of the present invention, the step of directing the first cutting fluids in a circumferential arc further comprises directing the first cutting fluids in a circumferential arc of 180° or less.
In accordance with another aspect of the present invention, the step of positioning the second cutting torch relative to the first cut further comprises positioning the second cutting torch above the first cut.
In accordance with another aspect of the present invention, the step of positioning the second cutting torch relative to the first cut further comprises positioning the second cutting torch above the first cut a distance so as to make the tubing below the cut from the second cutting fluids fishable.
In accordance with still another aspect of the present invention, the cable is exterior of the tubing.
As shown in
A second cutting torch 25, or tubing cutting torch, is lowered into the tubing 11 and positioned above the first cut 23 (see
The present invention will now be discussed in more detail. The two torches 19, 25 will be described, followed by the cutting operations.
The tubing 11 can be production tubing, although it can be other types of pipe or tubing.
The cable 15 can be an electrical line, a hydraulic line, a mechanical cable, etc. The cable is typically located outside of the tubing as exterior-rigged cable is more difficult to cut than cable in the interior of the tubing. Exterior-rigged cable is effectively shielded from a cutting torch by the tubing itself. The cable 15 is attached to the tubing by a strap or by clamps (not shown) at intervals along the length of the tubing. The cable 15 is typically in contact with the tubing along the length of the tubing. Typically, the approximate location of the cable on the circumference of the tubing is known.
The cable cutting torch 19 is shown in
The ignition section 43 contains an ignition source 49. In the preferred embodiment, the ignition source 49 is a thermal generator, previously described in my U.S. Pat. No. 6,925,937. The thermal generator 49 is a self-contained unit that can be inserted into the extension member. The thermal generator 49 has a body 51, flammable material 53 and a resistor 55. The ends of the tubular body 51 are closed with an upper end plug 57, and a lower end plug 59. The flammable material 53 is located in the body between the end plugs. The upper end plug 57 has an electrical plug 61 or contact that connects to an electrical cable (not shown). The upper plug 57 is electrically insulated from the body 51. The resistor 55 is connected between the contact 61 and the body 51.
The flammable material 53 is a thermite, or modified thermite, mixture. The mixture includes a powered (or finely divided) metal and a powdered metal oxide. The powdered metal includes aluminum, magnesium, etc. The metal oxide includes cupric oxide, iron oxide, etc. In the preferred embodiment, the thermite mixture is cupric oxide and aluminum. When ignited, the flammable material produces an exothermic reaction. The flammable material has a high ignition point and is thermally conductive. The ignition point of cupric oxide and aluminum is about 1200 degrees Fahrenheit. Thus, to ignite the flammable material, the temperature must be brought up to at least the ignition point and preferably higher. It is believed that the ignition point of some thermite mixtures is as low as 900 degrees Fahrenheit.
The fuel section 47 contains the fuel. In the preferred embodiment, the fuel is made up of a stack of pellets 63 which are donut or toroidal shaped. The pellets are made of a combustible pyrotechnic material. When stacked, the holes in the center of the pellets are aligned together; these holes are filled with loose combustible material 65, which may be of the same material as the pellets. When the combustible material combusts, it generates hot combustion fluids that are sufficient to cut through a pipe wall, if properly directed. The combustion fluids comprise gasses and liquids and form cutting fluids.
The pellets 65 are adjacent to and abut a piston 67 at the lower end of the fuel section 47. The piston 67 can move into the nozzle section 45.
The nozzle section 45 has a hollow interior cavity 69. An end plug 71 is located opposite of the piston 67. The end plug 71 has a passage 73 therethrough to the exterior of the tool. The side wall in the nozzle section 45 has one or more openings 77 that allow communication between the interior and exterior of the nozzle section. The nozzle section 45 has a carbon sleeve 79 liner, which protects the tubular metal body. The liner 75 is perforated at the openings 77.
The piston 67 initially is located so as to isolate the fuel 63 from the openings 77. However, under the pressure of combustion fluids generated by the ignited fuel, the piston 67 moves into the nozzle section 45 and exposes the openings 77 to the combustion fluids. This allows the hot combustion fluids to exit the torch through the openings 77.
The openings 77 of the nozzle are arranged in a circumferential arc (see
The tubing cutting torch 25 is radial cutting torch and is shown and described in U.S. Pat. No. 6,598,679. The tubing cutting torch 25 is similar to the cable cutting torch 19, in that it has an ignition section 43, a nozzle section 45T and a fuel section 47. Referring to
The tubing cutting torch 25 is conventional and commercially available.
The method will now be described. Referring to
The cable cutting torch 19 is located some distance above the stuck point of the tubing 11.
The cable cutting torch 19 is ignited. If the torch is on an electric wireline, an electric signal is sent to ignite the torch. Other ways of igniting the torch include a battery with a trigger mechanism used in a slick line, pressure fired, or using a battery powered drive bar.
When the cable cutting torch 19 is ignited (see
After the cable 15 is cut, the cable cutting torch 19 is removed from the tubing 11. Then, the tubing cutting torch 25 is lowered into the tubing 11 and positioned above the first cut 23, as shown in
Once positioned, the tubing cutting torch 25 is ignited. Combustion fluids 27 exit radially from the torch 25 and cut the tubing wall 11 all around the circumference (see
Each of the torches can be provided with ancillary equipment such as an isolation sub and a pressure balance anchor. The isolation sub typically is located on the upper end of the torch and protects tools located above the torch from the cutting fluids. Certain well conditions can cause the cutting fluids, which can be molten plasma, to move upward in the tubing and damage subs, sinker bars, collar locators and other tools attached to the torch. The isolation sub serves as a check valve to prevent the cutting fluids from entering the tool string above the torch.
The pressure balance anchor is typically located below the torch and serves to stabilize the torch during cutting operations. The torch has a tendency to move uphole due to the forces of the cutting fluids. The pressure balance anchor prevents such uphole movement and centralizes the torch within the tubing. The pressure balance anchor has either mechanical bow spring type centralizers or rubber finger type centralizers.
Thus, the present invention provides the severing of tubing and associated cable in a reliable manner. Two cutting torches are used, one to cut the cable and the other to cut the tubing. Because one torch is used to cut through the tubing and the cable, there is no need to align a torch with an opening, as in the prior art. The second torch, which cuts the tubing, need only be located relative to the cut cable.
It may be that, after making the first and second cuts 23, 29, the lower end of the upper part 15U of the cable is attached to the upper end of the lower portion 11L of the tubing by one or more straps, clamps or other type of cable anchors. This is dependent on the spacing of the cable anchors and the distance of the second cut above the first cut. These cable anchors will yield or break when the upper portion 15U of tubing is pulled from the well.
Although in the description of the preferred embodiment, the second torch 25 is described as being located above the first cut 23, this need not be so. The second torch could be located below the cut cable, so that the second cut is below the first cut. If the upper portion of the cable 15U is attached to the lower portion 11L of tubing by one or two anchors, then the anchors are broken and the upper part of the cable 15U is freed from the lower portion 11L of tubing by pulling the upper portion 11U of tubing.
Although in the preferred embodiment the cable cutting torch is used before the tubing cutting torch, this need not be so. The tubing cutting torch can be used before the cable cutting torch. Once the tubing is severed, the upper portion 11U may become misaligned from the lower portion 11L so that the longitudinal axes are no longer co-axial. However, in some wells, the tubing may be stabilized in the well so that misalignment may not pose a problem. Alternatively, after severing the tubing, the cable cutting torch can be lowered until it comes close to or contacts the lower portion 11L of tubing, wherein the cable cutting torch is ignited near the bottom of the upper portion 11U of tubing.
The foregoing disclosure and showings made in the drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense.